Dual container wood burning stove



1951 D. E. HOWES ET.AL 2,543,289

DUAL CONTAINER WOOD BURNING STOVE Filed OCL. l'7, 1946 2 Sheets-Sheet lFeb. 27, 1951 D. E. HOWES ET AL 2,543,289

DUAL CONTAINER woon BURNING STOVE Filed Oct. 17, 1946 2 Sheets-Sheet PBY cz x w ATTORNEYS Patented Feb. 27, 1951 DUAL CONTAINER WOOD BURNINGSTOVE Douglas E. Howes and Frank G. Smith, Northfield, Vt., assignors toNorwich University, Northfleld, Vt., a corporation of VermontApplication October 17, 1946, Serial No. 703,810

This invention relates to wood burning stoves. It provides a stovestructure formed to use wood more efficiently than the wood burningstoves of the prior art. A useful reference stove for comparison is theone in Seeleys Patent No. 2,348,933 of 1944.

In prior art stoves of Seeleys type, the wood is put in a fuel magazine,a part burns to make heat. The burning wood also makes gases bydistillation from the wood which is not burning. These gases are fedinto the heat of the combustion zone to make more heat in burning, andfinally the charcoal resulting fromdistilling gases from wood gets intothe combustion zone toburn to make more heat. This mode, of operationbroadly has been well known fora long time and Seeleys stove is only alate example of prior art efiorts to put this type of wood stove intomore general use than it has had.

The prior art wood stove has two objectionable operations which cause alot of trouble when used by the general public. The wood in the fuelmagazine is liable to burn faster than desired when the temperature ishigh enough not only to distill gases but also to burn them. When thistrouble is avoided by lowering the burning rate the combustion is liableto give a temperature to distill gases but not to fully burn them. Theproportion of gases unburned will condense in the stove or the stovepipe and the heating apparatus will progressively gum up resulting in avery messy condition. This is highly objectionable from the usersstandpoint. The average user of the stove is extremely likely to meetone or the other of these objectionable conditions, either because he isignorant of the stoves proper operation, or does not want to give itenough study and personal attention.

The stove of this invention is constructed to take care of itself andavoid both objections. It is also adapted to give other advantages aswill be pointed out. The way to provide the improved stove will beexplained from the example of the drawings.

In the drawings:

Fig. 1 is a front elevation of the stove;

Fig. 2 is a section on line 22 of Fig. 4;

Fig. 3 is a section on line 3-3 of Fig. 2; and

Fig. 4 is a section on line 44 of Fig. 3.

The stove indicated will first be considered in a form for use as asimple room heating stove particularly adapted for wood fuel.

The stove shell I with suitable insulatinglining 2 in the lower portion,Figs. 3 and 4, has ash pit doors 3 and. 4. with draft dampers 5 and i.

3 Claims. (Cl. 12673) The shell also has in the upper portion two pairsof doors I, 8 and 9, I0, each pair at different levels, Figs. 1 and 3. Asmoke pipe II is connected to the upper portion of a back extension l2,Fig. 4, on shell I to be explained.

Inside the shell slightly above the bottom is a horizontal plate [3. Itdivides the shell horizontally and is in the nature of a grate to holdwood on top. Ash pit space is that in the shell below plate E3. The ashpit space is divided by vertical wall 14 so that there is one ash pitwith door 3 and another with door 4. The dampers 5 and 6 in these doorseach control an air inlet to the corresponding ash pit. The air inletfor one ash pit is not an air inlet for the other. The plate l3 has twoslots I5 for one ash pit and two slots l6 for the other ash pit. Theseslots will pass air up and ash down through plate l3. This plate i3 ispreferably an air tight cross partition except for slots I5 and I6 andis not a type of shaking grate.

The top side of plate [3 will support a mass of Wood fuel in the shell.This wood may be put through doors 9 and I0, to fill the shell fromplate l3 up to these doors. are merely for convenience when one wantsaccess at a lower level than the level of doors 9 and ID. The whole massof wood in the shell is held by an inside partition wall ll of the shellin a vertically'divided condition of two columns of wood, one resting onplate l3 above one ash pit, the other column resting on plate 13 abovethe other ash pit.

The vertical partition wall ll runs from the top wall of the shell, Fig.2, down to a level some distance above horizontal plate l3. Wall E1 inthe shell I forms two vertical magazines A and B to hold the wood fed tothe stove, part in one and part in the other magazine. These twomagazines A and B are generally closed magazines from the top to thebottom but with both bottoms opening into a common space extendingacross the whole shell above plate l3. Fuel magazines A and B are thuspositioned to feed the Wood by gravity to a common space below them,intended for the stove combustion zone or zones as will be explained.The wall I! extends close enough to plate [3 to avoid a bridging of thewood between the two columns to interfere with the independent gravityfeed in each column to plate I3.

Extending across the rear wall of shell I is an air feeding pipe [8. Ithas an air damper 2| at one end and air damper 22 at the opposite end.

Pipe [8 has an inside cross wall 20. dividing it The doors I and 8 intotwo sections. When damper 2| is open, air outside the shell will feed inpipe i8 and into the combustion zone adjacent openings l9 from the pipel8. When damper 22 is open, air will feed to the combustion zoneadjacent openings 23 from the pipe l8. This is for feeding secondary airto these combustion zones and under damper control for each zone. Thisair feeding pipe l8, as seen in Fig. 3, is located adjacent the outletfrom the combustion space above the grate plate 13 as such outlet feedstoward the smoke pipe.

The stove shell I has the box-like extension i 2, shown in horizontalcross section by Fig. 4, and in vertical section by Fig. 3. Thisextension is in the nature of a radiator as will be explained. It hastwo vertical passages R and R separated by a partition 24. They arerespectively connected to the combustion space above plate It byhorizontal openings and d, Fig. 4, and to a common smoke pipe II at thetop of Fig. 3. The outline of this radiator extension from the front ofthe stove is indicated by dotted lines in Fig. 2. An ordinary damper eis indicated for opening (1 to shut off any draft up passage R. PassageR is not in use all of the time during stove operation while passage Ris used the entire time.

The stove in its simple form is used as follows: fuel magazines A and Bare filled with wood through doors 9 and H], which are then closed. Thedoors 9 and I 6 when closed become substantially air tight by use ofsuitable packing, not shown. Doors 1 and. 8 are used for convenience tostart the fire and. are normally closed and air tight. The fire may bestarted with combustion of wood at the bottom of magazine A, or bothmagazines A and B, with both their corresponding ash pit doors open andair feeding pipe [8 with all its openings feeding air in. However, sincethe idea of operation, in part, is to burn the wood of magazine A for acontinuously burning fire and burn the wood of magazine Bintermittently, the drafts to magazine B are now closed. This is not thewhole idea, however, and the remainder of the stoves mode of operationneeds special explanation.

When the structure described is considered it will be seen that thefollowing mode of operation is provided to use the wood fuelefiiciently. By opening damper in the ash pit, the wood from magazine Acan be kept burning with air supplied through openings It. This burningcan heat the whole stove. The products of combustion go out opening 0,Fig. 4, into radiator R to smoke pipe i I. Enough wood is kept burningcon-- tinuously in this way to maintain a temperature of about 1109 F.in the hot zone of the combustion space. The quantity of the heat isenough for slow distillation of the wood in both magazines A and B andalso for the stove to give off heat to a room for its primary heatinguse. The wood. in magazine B is kept from burning by keeping air awayfrom it, by keeping ash pit door 3 and its air damper 5 closed, so noair passes up through openings l5, Fig. 4, and keeping damper 22 closedto shut off air supply to openings 23. And damper e is preferablyclosed. The wood in magazine B is separated from that in magazine A onlyby partition wall ll. The close adjacency causes passage of heat frommagazine A to the wood of magazine B, which helps to distill combustiblegases from the wood in magazine B and helps avoid overheating the woodin magazine A, which would tend to create a run away, or too rapid,burning of the wood supplying the fire.

The gases from distillation of wood in magazine 13 pass down into thecombustion space. With damper e, Fig. 4, closed, the flow of these gasesis over to and above the hot zone of the combustion space. They areburned to make more heat in that hot zone. As the products of combustionfrom this zone pass through opening 0, Fig, 4, they are supplied withsecondary air through openings E9 of pipe I8 with damper 2i open for thepurpose. This secondary air helps complete the combustion of the gases,which may finish burning in radiator R and give oil their heat and enterthe smoke pipe i I with substantially no unburned wood gases left tocondense anywhere, as in the smoke pipe I i.

It will be seen from the foregoing that the whole stove full of wood canbe kept under constant distillation to get gases to burn and add theirheat to the heat from a relatively small wood burning fire and that thesmall wood fire is guarded against growing up progressively andundesirably into a run away fire from the large wood supply in thestove.

The rate of firing, using the wood fed by gravity from magazine A, asbefore stated, is at a high enough rate to cause the action of wooddistillation to make gases and charcoal. The charcoal soon afterstarting, is the fuel at the bottom of the magazine while wood is addedintermittently at the top to keep the small fire going. Considering onlythe fire supplied by the wood from magazine A, it will be clear that itsfiring and thus the heating rate of the stove may be varied from thatgiven by the distillation temperature to a progressively higher rate byprogressively increasing the air supply or draft for that fire. Thus thestove heat given by that fire alone may be varied.

The wood fuel fed into magazine B is held by that magazine as a reservesupply to provide for a much higher firing rate for the stove when it isdesired, as it is in severe weather. At any time desired the damper 5may be opened, also damper 22, and also damper c, all relating to thefuel in magazine B. When any damper combination setting supplies airthrough openings :5, Fig. 4, a fire is started using the wood orcharcoal of magazine B in addition to its gases. It joins the constantfire under magazine A and the two fires then become one fire on onegrate. simply a much larger fire with its automatic ravity feed of fuelto the fire so that now the stove is operating substantially as theSeeley stove of the prior patent or stoves of the same type willoperate. There is this difference, however, that the priorstoves willoperate only as a single fire. As stated before they are not properlycontrolled. They work too fast or not fast enough, having neithercontrol means to operate them at a minimum gas burning" temperature atall times nor means to vary their firing rate over the useful range ofthe new construction herein disclosed. In the new stove, when the largeor double fire is no longer needed, shutting off the air to omit supplyfor combustion under magazine B will cause a quick decrease of theheating rate for the stove. The charcoal at the bottom of magazine Bwill be sensitive to any lack of air supply, so the combustion at thebase of magazine B will die down rapidly as soon as its air supply isshut off by management of its dampers.

It should be noted that the new stove will take a large quantity of woodat one filling. In spring and fall weather this large filling willmaintain a wood fire for a long time before more Wood needed. Themagazine B is preferably made substantially larger than magazine A. Thelatter is made large enough to run its one fire a long time in mildweather to give all needed stove heat. The gases from wood in .magazineB will help the stove give enough heat at such time.

Assuming that the stove is dimensioned to give enough heat in mildweather from its operation as a base burner under magazine A alone, theair controls will then prevent a base burner operation under magazine B.The solid fuel in the latter will stand by ready for use when a higherrate of fuel firing is needed. When more heat is needed the air supplydampers will be opened to supply air for the large base burner fireunder magazine B. Then the air for the large fire Will be shut off, thelarge fire will quickly go out, but the small base burner fire willcontinue. In this way the central heating plant is operated at twofiring rates, having th call fire operating constantly under magazine Aand the large fire operating intermittently under magazine B and aresulting economy and efficiency in the use of wood fuel. Of course inmild Weather it is desirable to control the firing rate of the smallfire alone. It should be noted however that it is desirable to maintainthe small fire at a high enough rate to maintain a hot combustion zone,hot enough at all times to burn the gases of Wood distillation to avoidcondensation. These gases are made by heat distillation constantlyworking on the fuel of both magazines, that is, all the wood in thestove. It can easily b seen, that the dampers controlling air tomagazine A may be adjusted to maintain a zone of combustion in themagazine A at a temperature of about 100, or high enough to burn thewood gases as fast as they are generated in the stove. This temperatureis important to the operation in the stove combination of a constantlyoperated base burner with a second cas burner intermittently operated bythe expedient of closing its air intake and opening its combustionchamber to the combustion chamber of the constantly operating burnerduring periods when the latter only is operating, and by opening the airinlet to the intermittently operating burner and connecting itscombustion chamber to the chimney during the periods when both burnersare to be in operation. The provision for maintaining a fire at alltimes hot enough for burning the gases will avoid their condensation andan accumulation of gum in the heating apparatus. The provision of thisconstant hot burning zone will prevent a run away fire while permittinga relatively large quantity of wood in the stove. In this way the newstove structure is adapted to burn all the wood, gases, and charcoalfrom a full stove filling, but with more extended firing ratescontrolled to make the fuel last longer and he used more efiicientlythan prior art structures are adapted to do.

The magazine A is shown smaller than magazine B, which is a usefulprovision in most cases, particularly in getting a low firing rate limitrelative to a stove large enough to get a relatively high firing rate.In case of wanting only the advantage of a long heating operation ofabout the same firing rate, the magazines A and B may be of about thesame size. In some cases it would be useful to provide more than twomagazines. Each added one would then have the same operating arrangementwith magazine A as that described for B. Then when the fuel in magazineB is exhausted another one would be switched in for intermittent use inthe same manner.

6. Fuel in magazine A would need to be replenished, but that can be donewith a small amount, while the heavy work of replenishing fuel could bedelayed for a relatively longer time.

It will be clear that the control of the stove may be all, or part, ornot at all under automatic control with respect to the broadest aspectof the invention. The simplest case to consider is that of a handcontrolled stove embodying the structure adapted to carry out the woodburning operation. Suppose the simple stove is used to heat a one roomlog cabin in the woods. It will be very useful to the user in that itwill save him much labor in the getting and feeding of his wood fuelsupply. It will heat for many hours without requiring mor attention thanto open or close the drafts which control the intermittently operatedbase burner fire. The invention is adapted not only for that simple usebut likewise for a central house heating plant. The stov is clearly oneof economical construction with no parts for movable operation exceptdoors and dampers. It is a very low cost construction adapted for a muchimproved mode of operation in the use of wood fuel. The latter is madefeasible for use in many situations where before this invention, themore expensive coal or oil fuels would be used instead of wood. Thus theinvention helps close the competitive advantage of coal and oil fuelover woc-d fuel for house heating.

Having disclosed the new stove structure we claim as the invention:

1. A wood burning stove comprising a casing having a vertical heatconducting partition dividing the upper part of the chamber into twosubstantially air tight wood-receiving containers extending Verticallyadjacent each other in heat exchanging relation, a Wood-supporting gratewithin the casing and below the partition to form adjacent and connectedcombustion spaces, an individual chimney connection into each combustionspace, at least one separately controllable air inlet into eachcombustion space, and means for closing the chimney connection of one ofthe combustion spaces, whereby with the chimney connection and air inletof one of the combustion spaces closed the heat developed in the secondcombustion space will cause distillation of wood in the first combustionspace and its associated container resulting in distillation productswhich pass through and are consumed in the second combustion space.

2. A wood burning stove comprising a casing having a vertical heatconducting partition dividing the upper part of the easing intosubstantially airtight main and pilot wood-receiving containersextending vertically adjacent each other in heat exchanging relation,the partition being located nearer one side of the casing than the otherwhereby the main container is of substantially greater cross-sectionalarea than the pilot container, a wood-supporting grate within the casingand below the partition to form adjacent and connected main and pilotcombustion spaces, an individual chimney connection into each combustionspace, at least one separately controllable air inlet into eachcombustion space, and means for closing the chimney connection into themain combustion space, whereby with the main combustion space chimneyconnection and air inlet closed and those of the pilot space open theheat developed in the pilot combustion space will cause distillation ofwood in the main container and combustion space resulting indistillation products which pass through and are consumed in the pilotcombustion space, and with both main and pilot combustion spacesconnected to the chimney and air inlet the heat produced by the stovewill be increased.

3. A wood burning stove comprising a casing having a vertical heatconducting partition dividing the upper part of the casing intosubstantially air tight main and pilot wood-receiving containersextending vertically adjacent each other in heat exchanging relation,the partition being located nearer one side of the casing than the otherwhereby the main container is of substantially greater cross-sectionalarea than the pilot container, 2. wood-supporting grate within thecasing and below the partition to form adjacent and connected main andpilot combustion spaces, an individual chimney connection into eachcombustion space, a separately controllable air inlet below the grate ofeach combustion space, a second separately controllable air connectioninto each combustion space adjacent its chimney connection, and meansfor closing the chimney connection into the main combustion space,whereby with the main combustion space chimney connection and air inletclosed and those of the pilot space open the heat developed in the pilotcombustion space will cause distillation of wood in the main containerand combustion space resulting in distillation products which passthrough and are consumed in the pilot combustion space, and with bothmain and pilot combustion spaces connected to the chimmay and air inletthe heat produced by the stove will be increased.

DOUGLAS E. HOWES.

FRANK G. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

